Hopping conduction in doped silicon and germanium: Studies of their application as thermometers for X-ray calorimeters

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:50473

Zhang, J

This thesis covers experimental studies of the hopping conduction behavior of ion-implanted silicon (Si:P,B) and neutron transmutation doped (NTD) germanium, intended for use as the thermometer element of cryogenic microcalorimeters. The author measured the dc electrical conductivity of doped Si:P,B (both n- and p-type) with 5-50% compensation over the temperature range 0.05-30 K. In the ohmic region, their resistivities are consistent with the model of variable range hopping (VRH) with Coulomb gap in density of states at the Fermi level: {rho}(T) = {rho}{sub 0} exp(T{sub 0}/T){sup 1/2}. Deviations from this model were observed at the high and low temperature extremes. In the low temperature region, the resistivities show a stronger temperature dependence than the model prediction. The high temperature deviation appears to be consistent with a transition from Coulomb gap VRH to Mott VRH. The non-ohmic effect was studied in hopping conduction of ion-implanted Si:P,B and NTD Ge:Ga,As over a temperature range of 0.05-0.8 K for weak to moderately strong electric fields. The samples have T{sub 0}`s in the range of 1.4-60 K for Si, and 22-60 K for Ge. The non-ohmic data is compared with exponential and `sinh` field effect models: {rho}(E) = {rho}(O)e{sup {minus}x} and {rho}(E) = {rho}(O)x/sinh(x) (x{equivalent_to}eE{lambda}/kT), and an empirical `hot-electron` model. None of these provides an adequate fit to all of the data. The exponential field effect model represents the data better for the samples with higher T{sub 0} and at lower T. The `sinh` model can match the data only in a low field region. The `hot electron` model, although not justified by any non-ohmic hopping conduction theory, fits the data well for the silicon samples in the low T{sub 0} and high T regime.

• Research Organization: Wisconsin Univ., Madison, WI (United States)
• OSTI ID: 50473
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
CALORIMETERS
ELECTRIC CONDUCTIVITY
GERMANIUM
SILICON
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0013-0065 K
THERMOMETERS
X RADIATION